Field of the Invention
The present invention relates to a device and method for end-point monitoring used in the polishing of components, in particular semiconductor components.
The determination and monitoring of layer thicknesses is an indispensable aid for process control and process monitoring in the production of semiconductor components. Thus it is possible, for example in chemical/mechanical polishing (CMP), to measure the layer thicknesses of components, for example of wafers, on-line during processing.
Such layer thickness determinations may be carried out using ellipsometers or by interferometry.
In the context of interferometry, laser interferometry, for example, may be used. In order to determine the layer thickness, the wafer is scanned through the polishing pad or polishing cloth used in the CMP process. The polishing pads or cloths are constructed in such a way as to transmit light. Normally, pads or cloths which include a plurality of layers are used, in which pads or cloths a window which is transparent to the light wavelengths is adhesively bonded. Such a pad or cloth is illustrated in FIG. 1 and is explained in more detail in the description of the figures. The production of the pads and cloths entails correspondingly high costs and, moreover, with increasing abrasion of the pad or cloth may lead to a high level of defects. Consequently, the pads or cloths have to be exchanged frequently, with the result that the method for end-point monitoring is relatively time and cost intensive.